Centrifugal pump, more particularly that employed in hydraulic propulsion



D. V. HOTCHKISS. GEN-TRIFUGALPUMP, MORE PARTICULARLY .THAT EMPLOYED IN HYDRAULIC PROPULSION;

2 2 n m m A 2 w 7 J m U m r 0 M 30f 8 J w j O 5 2 m n 1 APPLICATION FILED .|ULY12,1920.

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UNITED STATES PATENT OFFICE.

DONALD VIVIAN HOTCHKISS, 0F HELENSBURGH, SCOTLAND.

Specification of Letters Patent. Patented Ja 24 1922 Application filed July 12, 1920. Serial No. 395,748.

(GRANTED UNDER THE PROVISIONS OF THE ACT OF MARCH 3, 1921, 41 STAT. L, 1313.)

T 0 all wlzom it may concern Be it known that I, DONALD VIVIAN HoTcHKiss, of Helensburgh, Scotland. a subject of theKing of Great Britain. have invented certain new and useful Improvements in and Relating to Centrifugal Pumps. More Particularly Those Employed in Hydraulic Propulsion, (for which I have filed application in England Jan. 7, 1919; Jan. 29, 1919; and July 7, 1919; Patent No. 134,428,) of which the following is a specification.

This invention relates to improvements in centrifugal pumps, more particularly to those employed in hydraulic propulsion, and has for its object the provision of means whereby a considerable hydrostatic head, greater ease of manipulation, higher duty and more certainty of operation may be obtained than with known forms of pumps.

The invention consists in the arrangement of a non-submerged. horizontally disposed, shrouded impeller of special form within a discharge chamber, said chamber being partly filled with air under pressure and partly filled with the fluid being pumped. The impeller is adapted to receive the fluid to be pumped. transmit it as streams while it is in co-active association therewith, and deliver it. under the action of centrifugal force. as a thin sheet of fluid into proximate receiving means which divide it into a plurality of tangential streams whose velocity is lowered and re-directed to a delivery chamber.

To reduce the friction between the structure and the fluid due to relative motion as much as possible. air injection may be provided.

In order that the invention may be the better understood. I will now proceed to describe the same in relation to the accompanying drawings, reference being had to the letters and figures marked thereon.

Like letters refer to like parts in the various figures, in which Fig. 1 illustrates in sectional elevation, one form of construction in accordance with this invention, the section being taken on the line l-1 of Fig. 2.

Fig. 2 is a view illustrating the impeller and tangential receiving means drawn to a smaller scale than Fig. l.

.peller a.

Fig. 3 is a section of Fig. on the line 3-3 drawn to a smaller scale.

Referring to the drawings, the impeller a. in Figs. 1 and 2 comprises a pan shaped member I) having radially disposed blades 0, a central boss d and a driving shaft 6, the passages 7' between the blades 0, 0 being of substantially constant area. The passages f communicate with a central feeding eye 9 which is supplied with the fluid to be pumped from a feeding chamber hof volute form, the chamber it being provided with a suct1on orifice z'. The pan-shaped member b is formed with an upstanding edge or lip Ia which acts as a shrouding and compels the fl lid emerging from the passages f to be discharged as a thin'sheet over the edge 70 when the impeller 11 is rotated. This thin sheet of fluid is received by a plurality of passages Z formed in the receiving chamber m by a plurality of dividing partitions n which are so arranged that the surfaces 0 thereof are substantially tangential to the periphery of the impeller a. By this means the sheet of fluid passing over the edge is of the member 6 of the impeller a is divided into a plurality of tangential or substantially tangential streams whose velocity head is, by reason of the expanding character of the passages Z between the partitions n, converted mostly into pressure head, the streams being diverted downwards into the chamber p where they unite and are delivered as a single stream from the discharge orifice g. Owing to the dome formation of the outside shell of the pump, the passages Z naturally curve downwards until a vertical portion is reached, and at this point, where the total area of the passages is as great as, or greater than, that of the impeller eye 9 the passages end.

Air is drawn into the eye g of the impeller a. through a passage 8 formed in the vertical shaft, and rising through the water in the impeller a, reaches the dome chamber 1* above it. Alternatively the air supply may be forced intothe impeller chamber a or the induction pipe by means of a pum or other compressing device. A pocket 0 air which effectively clears the chamber a of rotating liguid is'thus formed above the imwing to the ejector action of the water leaving the impeller a and entering the passages Z, a certain amountof air is being driven continuously through the passages with the water, and on leaving the passages, this air, by the' force of gravity. rises to the surface of the water in the annular chambert formed by the' bowl t of the impeller chamber and the inner shell casing under the passage Z. Small holes a are drilled in the bowl t forming the impeller chamber, or alternatively float valves may be fitted at the highest convenient positions, and this air is forced through the holes or valvesinto the annular space between the impeller a and the impeller bowl casing 2.

It will be noticed that the pressure in thepressure chamber t is greater than that in any other part of the pump as it is the sum of the'centrifugal head in the impeller a, and the head developed from the conversion of the velocity head into pressure head, by the action of the passages Z.

As the air enters the annular space around the impeller a, the water is forced out through the clearance w between the impeller a and the base of the pump. Owing to the lip is on the impeller a, no air can escape into the space above the impeller (6 without overcoming the impeller head or pressure, therefore driving out the water, the air followsthrough the clearance 10 and is returned to the chamber a by the impeller a.

Any excess of air sucked into the pump escapes through the discharge orifice 1 or alternatively, may be drawn off through an air escape pipe (not shown). The foregoing description will make clear that the air in the pump eliminates disc.-friction and dead-Water and acts as a lubricant to the water passing through the passages.

An automatic feeding device for supplying air in the quantity required may also be incorporated.

The output and power vary with the speed of rotation, and the pump may be controlled by variation of the speed of the prime mover, as in other pumps, also control may be economically effected by variation of the head against which the pump is ,'working. variation of the back pressure being brought about by any convenient method such as alteration of the length of head of water to be pumped, or, as in the case of ship propulsion, by varying the sectional area of the jet or jets. In practice. if the jets are closed and the flow of liquid through the pump prevented, the centrifugal head in the impeller a only, is maintained, the impeller a revolves without absorbing further power than the frictional losses of the bearings, and although the water seal be tween the impeller a and the passages Z is broken. the impeller a remains primed. Further, a jet of small area, by reason of the restricted flow of liquid through the pump,

reduces the power required from the prime mover. sincc less liquid is accelerated and there are little or no eddying losses.

Obviously although an impeller (I having straight blades disposed radially has been described the said blades may be either curved or otherwise disposed as may be found desirable to suit conditions of use, further the receiving passages I may be formed of independent tapered tubes adapted to receive the fluid sheet and deliver it in substantially similar manner to that already described.-

'hen the pump above described is to be used for jet propulsion the feeding chamber ii. is supplied with water by one or more conduits of large cross section communicating with the external water.

Having now fully described my invention what I claim and desire to secure by Letters Patent is 1. In a centrifugal pump, the combination of a bowl-shaped impeller casing formed with a central inlet and an annular discharge, a pan-shaped impeller rotatably mounted within said casing so as to leave an annular space therebetween, said impeller having a central inlet for the fluid to be pumped and an annular sbrouding over which the. fluid passes to the discharge of said casing, means for supplying air to said casing to form an air-pad. and means for supplying air under the pressure of tho pumpto the space between said casing and said impeller.

2. In a centrifugal pump, the combination of a. bowl-shaped impeller casing formed with a central inlet and an annular discharge. tangcntial blades within said discharge, a pan-shaped impeller rotatably mounted within said casing so as to leave an annular space therebetwcen, said impeller having a central inlet for the fluid to be pumped and an annular sbrouding over which the fluid passes to the discharge of said 'asing, means for supplying air to said casing to form an air-pad therein above said impeller and means for supplying air under the pressure of the pump to the space between said casing and said impeller.

3. A centrifugal pump comprising, in combination, a pump casing formed with a feed chamber and an impeller chamber. a coned impeller in said impeller chamber, having an annular sbrouding over which the pumped fluid is discharged as a thin sheet, means for dividing said sheet of fluid into a plurality of tangential streams, and means for supplying air to said impeller chamber to reduce disc-friction.

4. A centrifugal pump comprising in combination a pump casing formed with a feed chamber and an impeller chamber, a casing Within said impeller chamber forming an annular discharge space therebetween, tangential blades within said space, an im- 13c said chamber, and a pan-shaped impeller.

rotatable within said casing, said impeller having an annular upstanding edge constituting a shrouding over which the fluid raised by the impeller passes to said annular discharge.

6. A centrifugal pump comprising, in.

combination, apump casmg formed with a volute feeding chamber and a superposed impeller chamber, a bowl-shaped casing within said impeller chamber having an outwardly and downwardly flared flange forming an annular discharge with the wall of said chamber, a pan-shaped impeller rotatable within said casin said impeller having an annular upstan ing edge constitutin a shrouding over which the fluid raised by the impeller passes tosaid annular discharge, and-means for supplying air to said impeller chamber to form an air-pad therein when the pump is in operation.

7. A centrifugal pump comprising, in combination, a pump casing formed with a volute feeding chamber, a bowl-shaped casing within said impeller chamber having an outwardly and downwardly" flared flange forming anannular discharge with the wall of said chamber, substantially tangential blades in saiddischarge, and a pan-shaped impeller rotatable within said casing, said impeller having an annular upstanding edge constituting a shrouding over which the fluid raised'by the impeller passes to said annular discharge.

8. A centrifugal pump comprising, in combination, a pump casing formed with a volute feeding chamber and a superposed impeller chamber, a bowl-shaped casing within said impeller chamber having an outwardly and downwardly flared flange forming an annular discharge with the wall of said chamber, substantially tangential' blades in said discharge, a pan-shaped im-' peller rotatable within said casing, said impeller having an annular upstanding edge, constitutin a shrouding over which the fluid raised by t e impeller passes to said annu lar discharge, and means for supplying air to said impeller chamber to form an airpad when the pump is in operation.

9. A centrifugal pump comprising, in, combination, a pump casing formed with a volute feeding chamber and a superposed impeller chamber, a bowl-shaped impeller casingwithin said chamber and having an outwardly and downwardly flared flange forming an annular discharge with the wall of said chamber, an impeller rotatably mounted within said impeller casing so as to leave an annular space therebetween, said impeller having an annular shrouding over which the pumped fluid passes to said annular discharge, means for supplying air to said impeller chamber to form an air-pad therein when the pump is in operation, and means for supplying air under pressure of the pump to the space between said impeller casing and said impeller.

10. A centrifugal pump comprising,- in combination, a pump casing formed with a volute feeding chamber and a superposed impeller chamber, a bowl-shaped impeller casing within said chamber and" having an outwardly and downwardly flared flange forming an annular discharge with the wall of said chamber, substantially tangential blades within said discharge, an impeller rotatably mounted within said impeller casing so as to leave an annular space therebetween, said impeller having an annular shrouding over which the-pumped\fluid passes to said annular discharge, means for supplying air to said impeller chamber to form an airpad therein when the pump is in operation, and means for supplying air underspressure of the pump to the space between said impeller casing and said impeller.

11'. A centrifugal pump comprising, in combination, a pump casing formed with a feed chamber and an impeller chamber, an impeller casing in said chamber formin an annular discharge space with the wa thereof, tangential blades in said space, an impeller/rotatable within said impeller casing so ,as to leave an annular space therebetween, means for supplying air to said impeller chamber above said impeller and means for supplying air under pressure of the pump to the annular space between said impeller and said impeller casing.

In testimony whereof I-afiix my signature in presence of two witnesses.

DONALD VIVIAN HOTCHKISS.

Witnesses:

E. C. WALKER, J. P. CRAWLEY. 

